What is a potential risk of installing shingles over existing ones without proper precautions?

Installing shingles over existing ones without proper precautions can significantly increase the risk of leaks. This is primarily because the underlying materials may not be adequately inspected or prepared to handle the additional layer. If there are any pre-existing issues, such as damaged shingles or compromised underlayment, these can be exacerbated when new shingles are laid on top. Furthermore, the additional layer may prevent proper sealing and drainage, creating opportunities for water infiltration during rain or storms. Proper installation methods typically include removing old shingles to examine the roof deck for damage and ensuring that the surface is adequately prepared to receive new shingles.

Other potential concerns like increased weight and structural integrity should not be overlooked, as they could lead to problems over time, but the direct association with leaks makes this a critical issue to address during roofing projects. Improved insulation and aesthetic appeal are generally not benefits of overlaying old shingles, as those factors are more contingent upon the condition and quality of the installation rather than simply adding weight to the roof.